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Metformin is a biguanide oral hypoglycaemic which suppresses appetite.
Metformin is first-line drug treatment for overweight patients with type 2 diabetes
(1) in whom diet and exercise treatments have failed.
The principle advantage
of metformin treatment is that glycaemic control is improved but with significantly
less weight gain than when sulphonylureas are used (2).
It is unlikely
to cause hypoglycaemia.
Metformin is contraindicated if there is liver,
kidney or heart failure, or in patients with a very high alcohol intake because
of the perceived risk of serious lactic acidosis.
- however studies
by Salpeter et al concluded that the use of metformin in type 2 diabetes does
not increase the risk for fatal or non-fatal lactic acidosis or increase in blood
lactate concentrations compared with placebo or other hypoglycaemic treatments
- a commentary in the Evidence Based Medicine journal concerning
this study stated...'in contrast to phenformin, no credible evidence exists that
metformin increases the risk for lactic acidosis beyond what would be expected
from underlying diseases' (5)
- this gap between evidence and
prescribing guidelines makes management decisions difficult for the clinician
- a clinician must therefore make decisions in the context of evidence, his or
her own clinical experience and expertise in this area, prescribing guidelines
and the summary of product characteristics
Note that NICE guidance
(6) states that:
- review the dose of metformin if the serum creatinine
exceeds 130 micromol/litre or the estimated glomerular filtration rate (eGFR)
is below 45 ml/minute/1.73-m2.
- stop the metformin if the serum creatinine
exceeds 150 micromol/litre or the eGFR is below 30 ml/minute/1.73-m2
summary of product characteristics should be consulted before prescribing this
- Lancet (1998), 352, 854-65.
Journal (2000), 40 (1), 38-48
S et al (2002). Risk of fatal and nonfatal lactic acidosis with metformin use
in type 2 diabetes. Cochrane Database Syst Reve: CD002967 (latest version 27 Feb
S et al (2003). Risk of fatal and nonfatal lactic acidosis with metformin use
in type 2 diabetes mellitus: systematic review and meta-analysis. Arch Intern
- Evidence based Medicine (2002), 7(6),176.
NICE (May 2008). Management of
type 2 diabetes.
Last reviewed 06/2019